890 THE PALEONTOLOGY OF MINNESOTA. 



LBucanla rusatina. 



Formation and locality. Trenton group (Middle Nashville), DeKalb county. Tennessee. A small 

 imperfect specimen, possibly of this or the next species, occurred in the Clitambonites bed near Cannon 

 Falls, Minnesota. 



Collections. Prof. J. M. Safford; E. O. Ulrich. 



BUCANIA RUGATINA, W. Sp. ( Ulrich.) 

 PLATE LXVI, PIGS. 13-15. 



Resembles B. lindsleyi closely, but is smaller, the hight of what appears to be a 

 full-grown individual being a trifle less than 20 mm. Of other differences we may 

 mention that the whorls are more tightly enrolled, causing the umbilicus to be 

 appreciably smaller, the transverse markings are relatively stronger, more equidis- 

 tant, closer, averaging 1 mm. apart and appear more like waves or wrinkles than 

 overlapping plates. A slight groove on each side of the slit-band occurs on the 

 specimen illustrated. The other specimens are not in condition to permit us to 

 decide whether these grooves are characteristic of the species or not. At any rate 

 nothing of the kind has been observed on good specimens of B. lindsleyi. 



Formation and locality. Upper part of Trenton group, near Burgin, Kentucky, 

 Collection. E. O. Ulrich. 



BUCANIA NASHVILLENSIS, n. sp. (Ulrich.) 



PLATE LXVI, FIGS. 36-40. 



This species is based on six specimens received from Prof. J. M. Safford and 

 supposed by him to belong to his species lindsleyi. A careful comparison with the 

 original type of that species, good figures of which are given on plate LXVI, proves 

 that they represent a closely related yet distinct species. In the first place the 

 volutions expand more rapidly, two and a half turns making as large a shell as 

 three whorls in the lindsleyi. Next the umbilicus is smaller and more abrupt, the 

 sides of the volutions being more sharply rounded. Again the dorsum is more 

 prominent along the central line, causing a more or less decided flattening of the 

 dorso-lateral slopes. The slit-band also, instead of being sunken, is slightly raised. 

 Finally, as regards the surface markings, the transverse lines are much less regular, 

 and crowded rather than distant, while as a rule they would scarcely be described 

 as lamellose. They are also much less distinct except near the aperture of large 

 specimens where they are strengthened and emphasized, as usual with old shells, by 

 irregular wrinkles. The oblique revolving lines also are little more than half as 

 strong, while in the umbilical cavities, where these lines are usually very conspicu- 

 ous in Saflord's species, they are scarcely distinguishable. After adding to these 

 differences that the shell of B. nashvillensis is thicker, we believe we have given 

 ample reasons for the creation of a new species. 



